This invention relates generally to an apparatus for regulating the delivery of hot air in the tuyere stock of a shaft furnace; the tuyere stock consisting of an articulated pipe connecting a circular or annular supply conduit to a nozzle and being provided with an internal refractory lining. This invention also relates to a tuyere stock having the air feed regulating apparatus incorporated therein.
It is well know that the combustion and reduction processes in a shaft furnace, particularly in a blast furnace, are maintained by means of hot air and solid or liquid fuel which are injected through a series of tuyeres in the furnace structure, i.e., hearth of the furnace. However, the hot air is not distributed uniformly among the different tuyeres, due to a lack of symmetry in the fusion zone of the furnace. This asymmetrical fusion zone is caused by uncontrolled descent of material (non-uniform material distribution) into the furnace which creates different pressure losses opposite the respective tuyeres thus leading to a variation in the feed rate of hot air from one tuyere to another. As a result, the feed rate of hot air from one tuyere to another may thus differ by between 20 and 100%. Consequently, as the combustible materials (fuels) are burnt with the oxygen from the hot air, their injection rates have to be regulated in accordance with particular feed rates through each particular tuyere.
Measuring the delivery or feed rate in each of the tuyere stocks permits the determination of those places wherein the admission of hot air is more intensive (high feed rate) or less intensive (low feed rate). By reducing the unnecessarily high rates of feed, therefore, excess hot air from more intensive tuyeres may be guided towards those tuyeres with a low rate of feed. In other words, if the hot air feed rate can be regulated or modified, than the less active tuyere locations may be stimulated such that the furnace may operate more uniformly regardless of the non-uniform material distribution of the furnace (i.e., asymmetrical fusion zone). The resulting furnace would thus function more efficiently and under more satisfactory conditions.
Unfortunately, the prior art has no effective or practical means of regulating the feed rate of hot air from a tuyere stock into a tuyere. It is a object of the present invention to address this deficiency in the prior art as will be discussed in more detail hereinafter.